1. Field of the Invention
The present invention relates to a rotary head assembly, and more particularly to a rotary head assembly used in a helical-scanning-type magnetic recording and reproducing apparatus used with a magnetic tape.
2. Description of the Related Art
FIGS. 4A and 4B are used to illustrate a conventional helical-scanning-type magnetic recording and recording apparatus. More specifically, FIG. 4A is a perspective view of a rotary drum, and FIG. 4B is a schematic view illustrating a recording operation performed on a magnetic tape. FIGS. 5A and 5B are used to illustrate a thin-film magnetic head used in a magnetic recording and reproducing apparatus such as a hard disk apparatus. More specifically, FIG. 5A is a perspective view of the thin-film magnetic head, and FIG. 5B is a plan view of the main portion of the thin-film magnetic head shown in FIG. 5A. FIG. 6A illustrates a case where the thin-film magnetic head is used in a helical-scanning-type magnetic recording and reproducing apparatus. FIG. 6B illustrates a case where two such thin-film magnetic heads are used in the helical-scanning-type magnetic recording and reproducing apparatus. More specifically, FIG. 6A is a perspective view of a rotary head assembly in which the thin-film magnetic head is mounted to a base, and FIG. 6B is a development of the main portion of a side surface of a double-azimuthal-type rotary head assembly, in which the rotary head assembly of FIG. 6A is mounted to a rotary drum. FIG. 7 is a schematic view illustrating the movements of a magnetic tape recording surface and the magnetic heads when a recording/reproducing operation is carried out on the magnetic tape using the rotary head assembly of FIG. 6B. FIGS. 8A and 8B schematically illustrate a case where the magnetic tape is subjected to a recording operation and subsequently to a reproducing operation using the rotary head assembly of FIG. 6B. More specifically, FIG. 8A is an enlarged view of the main portion of FIG. 6B, and FIG. 8B is a schematic view illustrating the movements of the magnetic head recording surface and the magnetic heads when the magnetic tape is subjected to a recording operation and subsequently to a reproducing operation.
In a magnetic recording and reproducing apparatus, such as a VTR or a computer-data recording and reproducing apparatus, using a magnetic tape as a magnetic recording medium, a recording and a reproducing operation is carried out by helical scanning. Common helical-scanning-type magnetic recording and reproducing apparatuses use a plurality of heads to increase the recording density and data transfer rate. They come in various types. One such type is illustrated in FIG. 4A. In this type, a pair of magnetic heads H1 and H2 are disposed on opposite locations of a rotary drum D.
For example, single heads or combination heads may be provided. When single heads are provided one magnetic head H1 and one magnetic head H2 are provided. When combination heads are provided two magnetic heads H1 and two magnetic heads H2 are provided. Regardless of whether single heads or combination heads are used, when the rotary drum D is driven to subject a magnetic tape Tp to a recording operation using either one of the magnetic head H1 and the magnetic head H2 or either one of the pair of magnetic heads H1 and magnetic heads H2, guard bandless recording is carried out. When guard bandless recording is carried out, a track is subjected to recording so that the recording is carried out in an overlapping manner with respect to a portion of a different track that has just been subjected to recording by either one of the other of the magnetic head H1 and the magnetic head H2 or either one of the other of the pair of magnetic heads H1 and magnetic heads H2. For example, as shown in FIG. 4B, after a track T1 has been subjected to recording by the magnetic head H1, a track T2 is subjected to recording by a magnetic head H2 so that the recording is carried out in an overlapping manner with respect to a portion of a top end of the track T1.
When a recording/reproducing operation is carried out by helical scanning by single heads or by combination heads, an azimuthal recording/reproducing operation is carried out. In the azimuthal recording/reproducing operation, paths (or tracks) of magnetic gaps of the magnetic heads are disposed obliquely from a magnetic-tape-transporting direction, and the magnetic gaps in the magnetic heads are inclined by predetermined azimuth angles from a track widthwise direction. The azimuthal recording/reproducing operation carried out with single heads or combination heads is a double azimuthal recording/reproducing operation in which azimuth angles xcex81 and xcex82 of the magnetic gaps G1 and G2 in the respective magnetic heads H1 and H2 are formed by lines inclined in opposite directions, as shown in FIG. 4B. When the double azimuthal method is used, a track T1 to be subjected to a reproducing operation by the magnetic head H1 has an area overlapped by an adjacent track T2 which has been subjected to recording by the magnetic head H2. The double azimuthal method is carried out to eliminate crosstalk with the adjacent track T2 by making use of azimuthal loss in which the azimuth angle xcex81 of the track T1 and the azimuth angle xcex82 of the track T2 in this overlapping area have different sizes and are formed by lines extending in different directions. Similarly, when the track T2 is subjected to a reproducing operation by the magnetic head H2, azimuthal loss is made use of to eliminate crosstalk with the adjacent track T1. The azimuth angles xcex81 and xcex82 may be the same size.
Conventionally, MIG (metal-in-gap) heads, layered-type, heads, and the like have been used as magnetic heads in helical-scanning-type magnetic recording and reproducing apparatuses. In recent years, in order to achieve higher recording density of a magnetic recording medium in VTR and data recording and reproducing apparatuses, track widths have been made smaller and higher frequencies have been used. To decrease track widths, magnetic gap widths must be made smaller. However, in MIG heads, the magnetic gaps are formed by a cutting operation, making it difficult to make them smaller in size. Thus, track widths cannot be made smaller. In addition, to decrease track widths, abutting surfaces used to form magnetic gaps need to be polished with high precision. However, it is difficult to increase the precision with which the polishing is carried out in very small magnetic gaps. On the other hand, to make it possible to use higher frequencies, the inductance needs to be made low. However, in MIG heads and layered heads, the inductance cannot be made low. MIG heads and layered heads have the disadvantage that the reproducing operation output cannot be made large when higher recording density is to be achieved.
Various thin-film magnetic heads have already being used in magnetic recording and reproducing apparatuses, such as hard disk apparatuses. In general, there are two types of thin-film magnetic heads: inductive heads used primarily for recording operations, and magnetoresistive (MR) heads primarily used for reproducing operations. Composite-type thin-film magnetic heads in which such inductive heads and such magnetoresistive heads are placed upon each other into a layered structure are frequently used in magnetic recording and reproducing apparatuses. As shown in FIGS. 5A and 5B, in a thin-film magnetic head 1 used in a magnetic recording and reproducing apparatus such as a hard disk apparatus, a head element portion 3 and bonding pads 4 are formed at a side surface of a slider 2. The head element portion 3 comprises an MR head 3a and an inductive head 3b. The slider 2 is formed by cutting a wafer formed of a ceramic material such as aluminum oxide and titanium carbide (Al2O3.TiC). The inductive head 3b is placed on top of the MR head 3a to form a layered structure. The bonding pads 4 are connected to the MR head 3a and the inductive head 3b. The MR head 3a comprises an MR layer 3a1, an upper gap layer 3a2 formed on top of the MR layer 3a1, and a lower gap layer 3a3 formed closest to and below the slider 2. These three layers form a magnetoresistive (MR) element Ga. An upper shield layer 3a4 and a lower shield layer 3a5 provided above and below the MR element Ga so that the MR element Ga is disposed therebetween functioning as reproducing magnetic gaps during reproduction. The MR layer 3a1 detects any magnetic field that has entered the upper and lower shield layers 3a4 and 3a5.
The inductive head 3b comprises an upper core layer 3b1 and a lower core layer 3b2 also being the upper shield layer 3a4 of the MR head 3a. A nonmagnetic material layer 3b3 is formed between the upper and lower core layers 3b1 and 3b2 in order to form a recording magnetic gap Gb. A track width Tw at the magnetic gap Gb is determined by the length of the magnetic gap Gb in a longitudinal direction (or in a horizontal direction in FIG. 5B) thereof. The track width Tw is slightly longer (by approximately a few percent to slightly more than 10 percent but less than 20 percent) than the longitudinal length of the MR layer 3a1. The centers of the MR element Ga and the magnetic gap Gb as viewed in a direction of the track width Tw are made to lie on a centerline C. The MR element Ga and the magnetic gap Gb which are exposed from a top surface of the slider 2 form a layered structure, and are thus parallel to each other.
The four bonding pads 4, formed at a side surface of the slider 2, are connected to coils (not shown) of the inductive head 3b and the MR layer 3a1 of the MR head 3a by four leader wires (not shown).
Such a thin-film magnetic head can be mass-produced, and has the advantages of being small and being capable of providing high-precision recording and reproducing operations. The thin-film magnetic head makes it possible to easily carry out fine dimensioning, such as forming narrower gaps, to form tracks with smaller widths. As a result, it can provide high-density recording. In particular, an MR head can, regardless of its speed relative to a magnetic recording medium, directly respond to a signal magnetic field to provide a high reproducing operation output. In addition, the inductance value of an MR head is much lower than those of an MIG head and a layered-type head, so that it can be used with higher frequencies. To overcome the problems of such conventional magnetic heads, there has been a desire to incorporate the above-described thin-film magnetic recording heads in rotary heads and to apply them to a helical-scanning-type magnetic recording and reproducing apparatus used with a magnetic tape.
To apply the thin-film magnetic head 1 to a helical-scanning-type magnetic recording and reproducing apparatus used with a magnetic tape, it is formed so that the MR element Ga and the magnetic gap Gb are exposed from a side portion thereof, as shown in FIG. 6A. Then, it is mounted to a base 5. Circuit boards 6, such as flexible printed-wiring boards, connected to an external processing circuit are provided on the same surface of the base 5 as the thin-film magnetic head 1. Terminal portions 6a of the circuit boards 6 and the bonding pads 4 are connected by balls 7 formed by ball bonding, and the MR element Ga and the magnetic gap Gb are made to face an outer peripheral surface of the rotary drum D and are mounted at opposite locations of the rotary drum D, whereby a rotary head assembly is constructed. This rotary head assembly can be applied to the helical-scanning-type magnetic recording and reproducing apparatus.
Even when a recording/reproduction operation is carried out on a magnetic tape with the thin-film magnetic head 1, azimuthal recording and reproducing must be carried out. Therefore, as stated above, it is necessary to form the MR element Ga and the magnetic gap Gb so that they are inclined by corresponding azimuth angles from the track width direction. However, when the above-described thin-film magnetic head 1 is used in, for example, a hard disk apparatus, the MR element Ga and the magnetic gap Gb become perpendicular to the mounting surface of the base 5, so that, during a recording/reproducing operation using the thin-film magnetic head 1, they are perpendicular to tracks T, and thus have azimuth angles equal to zero degrees. The azimuth angles become zero degrees because the thin-film magnetic head 1 is formed by a manufacturing process in which layers are successively applied on top of a flat wafer. The same thing also applies to an MR element Gaxe2x80x2 and a magnetic gap Gbxe2x80x2 of another thin-film magnetic head 1 shown in FIG. 6B. In order to form azimuth angles at the MR element Ga and the magnetic gap Gb of the thin-film magnetic head 1 as well as azimuth angles at the MR element Gaxe2x80x2 and the magnetic gap Gbxe2x80x2 of another thin-film magnetic head 1, the base 5 to which the thin-film magnetic heads 1 are mounted is mounted to the rotary drum D by tilting it by a predetermined azimuth angle with respect to the rotary drum D by a suitable means, so that the magnetic head H1 and the magnetic head H2 are realized, as shown in FIG. 6B.
When a rotary head assembly in which, for example, the MR element Ga and the magnetic gap Gb of the magnetic head H1 are tilted by predetermined azimuth angles in the above-described way is used, the substantially center portions of the MR element Ga and the magnetic gap Gb in the trackwidth-Tw direction (or in the longitudinal direction) lie on the centerline C. Therefore, taking the magnetic head H1 shown in FIG. 7 as an example, the MR element Ga is displaced from the center of a track T1 in the track width direction which has been subjected to recording by means of the magnetic gap Gb.
When reproducing data from tracks T1 and T2, it is preferable that the center portions thereof in the track width direction be subjected to reproducing operations. When, with, for example, the MR element remaining displaced from the centers of tracks T1 and T2 to be reproduced, data is reproduced from tracks T1 and T2 to be subjected to the reproducing operation, edges of tracks T1 and T2 in the widthwise direction thereof are subjected to the reproducing operation, so that the reproducing operation output is reduced. With small width standards for tracks to be subjected to recording by means of the recording gaps Gb and Gbxe2x80x2 of inductive heads, and with large size standards for overlapping areas to be subjected to recording, the MR elements Ga and Gaxe2x80x2 may extend beyond tracks T1 and tracks T2 to be subjected to the reproducing operation. This reduces the record-signal reproducing operation output. Depending on the sizes of the azimuth angles xcex81 and xcex82, the distances between the MR element Ga and the magnetic gap Gb and between the MR element Gaxe2x80x2 and the magnetic gap Gbxe2x80x2, the longitudinal lengths of the MR elements Ga and Gaxe2x80x2, etc., the MR elements Ga and Gaxe2x80x2 may extend beyond the widths of tracks T1 and tracks T2 to be subjected to the reproducing operation. This reduces the record-signal reproducing operation output.
In double-azimuthal recording and reproducing operations, the MR element Ga of the magnetic head H1 and the MR element Gaxe2x80x2 of the magnetic head H2 may be displaced from a track-width center in different directions, or they may be displaced therefrom by different amounts. When, as shown in FIG. 6B, the magnetic heads H1 and H2 are mounted on the rotary drum D, they are mounted by making the end portions defining the recording magnetic gaps Gb and Gbxe2x80x2 lie on a center line H0, as shown in FIG. 8A. When these end portions of the MR elements Ga and Gaxe2x80x2 are positioned at different heights, a height difference H is produced.
In double-azimuthal recording and reproducing operations, after a track T1 has been subjected to recording by means of the magnetic gap Gb in the magnetic head H1, a recording operation is carried out in an overlapping manner with respect to a portion of the top end of the track T1 in order to subject a track T2 to the recording operation by means of the magnetic gap Gbxe2x80x2 in the magnetic head H2. Therefore, when data recorded near an edge of a track in a widthwise direction thereof is reproduced, the reproducing operation may be affected by an adjacent track signal. on the other hand, when data recorded on the center portion of a track in the widthwise direction thereof is reproduced, the reproducing operation output can be increased. However, as viewed from the recording surface side of the magnetic tape shown in FIG. 8B, even when, during a reproducing operation by the magnetic recording and reproducing apparatus, the location of the MR element Ga within track 1 is adjusted (or tracked) so that it is situated at the track-width center where the reproducing operation output becomes maximum, the MR element Gaxe2x80x2 reproduces data at a location which is displaced from the track-width center portion of track T2 by the height difference h. This reduces the output of reproduced signals recorded on the track T2.
The azimuth angle xcex81 of the MR element Ga and the magnetic gap Gb of the magnetic head H1 and the azimuth angle xcex82 of the MR element Gaxe2x80x2 and the magnetic gap Gbxe2x80x2 of the magnetic head H2 may cause the above-described problems regardless of whether the sizes thereof or inclinations thereof have the same standard values, or whether the standards of the magnetic heads H1 and H2 are different.
Accordingly, it is an object of the present invention to provide a rotary head assembly used in a helical-scanning-type magnetic recording and reproducing apparatus, which includes an MR head and an inductive head and which can provide a large reproducing operation output when an azimuth angle is provided at a magnetic gap in a thin-film magnetic head.
To this end, according to the present invention, there is provided a rotary head assembly comprising:
a plurality of thin-film magnetic heads with predetermined azimuth angles, each thin-film magnetic head including an inductive magnetic head and a magnetoresistive head placed upon each other to form a layered structure, each inductive magnetic head including a magnetic gap and each magnetoresistive head including a magnetoresistive element, each magnetic gap and each magnetoresistive element being mounted to an outer periphery of a rotary drum so as to be exposed therefrom;
wherein end portions defining the magnetic gaps of the inductive magnetic heads are positioned at a same height; and
wherein end portions of the magnetoresistive elements of the magnetoresistive heads are positioned at a same height.
Although not exclusive, the end portions defining the magnetic gaps of the inductive magnetic heads and the end portions of the magnetoresistive elements of the magnetoresistive heads may all be positioned at a same height.